What is the characteristic of a system that turns it into a chaotic system?

[Boyphys]

Is there a way to predict the positions of a double pendulum? What is the characteristic of a system that turns it into a chaotic system? I’ve always had this doubt!

 

[anuttarasammyak]

https://en.wikipedia.org/wiki/Double_pendulum

explains sentitivitiy to initial condition to flip as illustrated above. What kind of doubt do you have ?